The first altar mentioned in the Word was the one built by Noah after he came out of the ark, after being saved from the great flood. On that altar, he sacrificed clean animals to the Lord.

Mountains represent the Lord because of their height; we need to raise our thoughts above worldly things when "talking" with the Lord. An altar is a small artificial mountain. When it's used in worship, it can call to mind this raising of thought. The fire and smoke that rise from an altar are symbolically being sent to the Lord.

Most altars were made from unhewn stones. Stones represent truths. Unhewn stones - ones that have not been shaped by men - represent truths from the Word, truths that have not been adulterated.

The clean beasts to be sacrificed represent good things, charitable acts done because they are right. The clean birds represent thoughts about doctrine and actions, and about what is right. Presenting these things is an acknowledgment that we have them from the Lord, and a giving thanks to Him for them.

In the Israelitish Tabernacle, the altar of burnt offering represented the acknowledgment of good and the altar of incense that of truth. For this reason this larger altar, which was outside by the door, was made of brass which signifies natural good, while the altar of incense was made of gold, which signifies love to the Lord from whom comes truth.

6352. 'Simeon and Levi are brothers' means faith in the will and charity, but here the opposite since faith separated from charity is meant. This is clear from the representation of 'Simeon' as faith in the will, dealt with in 3869-3872, 4497, 4502, 4503, 5482, 5626, 5630; and from the representation of 'Levi' as charity, dealt with in 3875, 3877, but here the opposite of it since faith separated from charity is meant. For when such faith is represented by 'Reuben' as is evident from the explanations at verse 4, it follows that no faith present in the will, nor thus any charity, are what 'Simeon and Levi' represent; for these deficiencies follow in a chain of effects resulting from their initial cause. 'Simeon' therefore represents falsity in the will, and 'Levi' evil put into practice, for these are the opposites of faith in the will and charity. The fact that Simeon and Levi are cursed proves that those opposites are meant here.